00463nas a2200145   4500000000100000008004100001100001500042700001500057700001500072700001600087700001500103245018100118300001200299490000600311       1999                            d1 aM. Frisher1 aH. Heatlie1 aS. Chapman1 aJ. Bashford1 aJ. Norwood00aSwitching between metered dose inhalers (MDIs) and dry powder inhalers (DPIs) in airways disease: An analysis of agespecific rates using the general practice research database.  a253-2590 v2